1. Technical Field of the Invention
The present invention relates to telephone networks and, in particular, to the efficient monitoring of telephone calls within such networks by law enforcement agencies.
2. Description of Related Art
It is well known in the art for law enforcement agencies to tap telecommunications trunk connections for the purpose of monitoring voice conversations (calls). Telecommunications switches in the network are programmed with a stored list of telephone numbers assigned to subscribers whose calls are to be monitored. Whenever a switch handles a call connection having a calling party or called party identification number matching a number on the stored list, the switch requests the establishment of a trunk connection (comprising the "tap") with a monitoring center. If the request is granted, a tap trunk connection is established with the monitoring center and then connected (in a manner much like the formation of a conference or three-way call) into the subscriber call connection.
In many situations, switches in the network may attempt to set-up multiple tap connections with the monitoring center for the same call. For example, when the called party number is marked for law enforcement agency monitoring, and the made call to that called party utilizes (i.e., passes through) two different telecommunications switches, each switch involved in the call compares the called number to their stored lists, finds a match, and then requests establishment of a tap trunk connection with the monitoring center. Furthermore, in situations where the parties to a monitored call subsequently initiate a multi-party call (like a conference or three-way call, or a call forward), the switches involved in the various legs of that call find a match and may request the establishment of a tap trunk connection with the monitoring center for multiple ones of the included call legs. Because the communications (trunk) and monitoring (recorder) resources provided by the monitoring center are limited, it is preferred that instances of multiple requests for tap connections and redundant monitoring of the same call be eliminated.